Positive displacement pumps are widely used. Such pumps can comprise one or more pump chambers, each chamber having an inlet and an outlet. In use, the inlet and outlet can be sequentially opened and closed. In the known apparatus each pump chamber may be arranged with at least one displacement element, which can be moved by some sort of driving means arranged adjacent to the pump chamber. During its movement, the displacement element alternately carries out a suction stroke and a displacement stroke thereby increasing and reducing, respectively, the volume of the pump chamber.
In some prior art embodiments the pump chamber can have at least one flexible separating element which forms at least part of the side wall thereof and which functions to separate the displacement element from the fluid which is being pumped through the chamber.
Such displacement pumps are generally used in pump and/or compressor systems for pumping or displacing aggressive and/or abrasive media such as particulate slurries, or some corrosive liquids or gases which may be at high temperature or under high pressure. In one embodiment of a known displacement device, a certain amount of medium to be displaced is carried into the pump chamber via the inlet side (and from the pipe system) during the suction stroke of the displacement element, and this same amount of medium is displaced (or forced) out of the pump chamber via the outlet side during the displacement stroke of the displacement element.
The driving means, which impose a translating movement on the displacement element, may be a linear motor, a magnet drive, a hydraulic drive, a camshaft drive, an eccentric drive, a crank-connecting rod mechanism, etc. In normal operational circumstances, the displacement element undergoes a displacement stroke loaded by the working pressure and a non- or low-loaded suction stroke. As a result of this unbalanced application of forces, the constructional dimensions of the displacement element and its respective parts are geared to the loaded displacement stroke.
The object of the invention is to provide a displacement pump apparatus in which the load on the moving parts is significantly reduced.